Gas turbine combustor with fuel and air swirler

ABSTRACT

A nozzle cap ( 10 ) is disposed downstream of a nozzle body ( 1 ) of a combustor for a gas turbine, an inner surface part ( 12 ) of which is of a conical shape diverging downstream to define a fuel-jet guide ( 17 ) for guiding fuel jet ejected from one or more nozzle holes ( 3 ) provided at the center of a downstream end surface of the nozzle body. Fuel ejected from the one or more nozzle holes smoothly runs along the fuel-jet guide without remaining there to join with a swirl stream (S) in a swirl path ( 9 ), and to burn without generating smoke. Air introduced into a first auxiliary air path ( 6 ) defined between the nozzle body and a partition ( 5 ) at a position upstream thereof passes through a second auxiliary air path ( 16 ) defined between a downstream end surface ( 2 ) of the nozzle body ( 1 ) and an upstream end surface ( 13 ) of the nozzle cap and reaches an entrance ( 19 ) of the fuel-jet guide. The air then flows along the fuel-jet guide to cool the nozzle cap and prevent the fuel ejected from the one or more nozzle holes from sticking to the nozzle cap.

TECHNICAL FIELD

The present invention relates to a combustor for a gas turbine.

BACKGROUND ART

As is well known, a combustor for a gas turbine is adapted so that afuel ejected from one or more nozzle holes of a nozzle body is mixedwith swirling air blowing from a swirl path formed around the nozzlebody.

Particularly, when the nozzle body is of a cylindrical columnar shapehaving a wall at a tip end, i.e., a downstream end, and the one or morenozzle holes is located at the center of the downstream end wall as in acase of a pilot combustor, the swirl air flowing along the outercircumference of the nozzle body separates therefrom at the periphery ofthe downstream end wall of the nozzle body and generates circulationvortices into which the fuel ejected from the one or more nozzle holesis involved. This causes a problem in that smoke may be generatedbecause the fuel burns while remaining therein (see FIG. 2).

The present invention has been made to solve the above-mentionedproblem, and an object thereof is to provide a combustor for a gasturbine wherein fuel, ejected from the one or more nozzle holes at thecenter of a downstream end wall of a nozzle body is mixed with swirlingair blowing from a swirl path formed around the nozzle body, is burntwithout remaining near the one or more nozzle holes to prevent smokefrom being generated.

DISCLOSURE OF THE INVENTION

According to the present invention, provision is made of a combustor fora gas turbine, wherein fuel ejected from one or more nozzle holes at thecenter of a downstream end wall of a nozzle body is mixed with swirlingair blowing from a swirl path formed around the nozzle body. Thecombustor is characterized in that a nozzle cap of a generally conicalshape diverging downstream from the one or more nozzle holes in a nozzlebody is provided. According to the combustor for a gas turbine of such atype, the fuel ejected from the one or more nozzle holes flows along thenozzle cap without remaining thereon.

Preferably, the downstream end of the nozzle cap is united with theinner wall of the swirl path so that the nozzle cap forms a fuel-jetguide for smoothly guiding the fuel ejected from the one or more nozzleholes into the swirl path.

Also, a path for directing cooling air toward the one or more nozzleholes may be provided at the upstream end of the nozzle cap so that thenozzle cap is cooled by a flow of the cooling air along the fuel-jetguide to prevent fuel mist from sticking to the fuel-jet guide.

Further, a partition may be provided between the swirl path and acircumference of the nozzle body to define a narrow path between thecircumference of the nozzle and the partition, the downstream end of thenarrow path being connected to the upstream end of the cooling air pathto take in cooling air from the upstream of the narrow path.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a structure of one embodiment of acombustor for a gas turbine according to the present invention; and

FIG. 2 is an illustration of a structure of a conventional combustorhaving no nozzle cap.

BEST MODES FOR CARRYING OUT THE INVENTION

FIG. 1 illustrates a combustion chamber, in a combustor for a gasturbine, for forming a so-called pilot flame for igniting a main mixturegas which was formed by preliminary mixing of fuel and air.

A nozzle body 1 of a generally cylindrical columnar shape is provided ata center of a downstream end surface 2 with the one or more nozzle holes3 (only position thereof is indicated) from which is ejected fuel. Atubular partition 5 is spaced outside a circumference 4 of the nozzlebody 1 to define a first auxiliary air path 6 between the same and thenozzle body 1.

An outer tubular body 8 is arranged outside the tubular partition 5 viaa swirler 7 to define a swirl path 9 between the tubular partition 5 andthe outer tubular body 8. Air introduced into the swirl path 9 at anupstream position, not shown, passes through the swirler 7 and isconverted to a swirling stream having rotating force as indicated by S.Air is also introduced into the first auxiliary air path 6 at anupstream position, not shown.

A nozzle cap 10 is provided downstream of the nozzle body 1 which has anouter surface part 11 and an inner surface part 12 both connected toeach other by an upstream end surface 13 and by a downstream edge 14.

The outer surface part 11 of the nozzle cap 10 and an outer surface ofthe tubular partition 5 are flush with each other, and an upstream end15 of the outer surface part 11 of the nozzle cap 10 is connected to adownstream end of the tubular partition 5. However, a gap is formedbetween the upstream end surface 13 of the nozzle cap 10 and adownstream end surface 2 of the nozzle body 1 to define an annularsecond auxiliary air path 16. The second auxiliary air path 16communicates with the first auxiliary air path 6 around the outsidethereof.

The inner surface part 12 of the nozzle cap 10 is of a conical shapediverging downstream to define a fuel-jet guide 17 for guiding fuel jetejected from the one or more nozzle holes 3 of the nozzle body 1. Thefuel-jet guide 17 has an entrance 19 defined by an upstream end edge 18of the inner surface part 12 of the nozzle cap 10 and an exit 20 definedby a downstream end edge 14 thereof.

Fuel ejected from the one or more nozzle holes 3 of the downstream endsurface 2 of the nozzle body 1 runs along the fuel-jet guide 17 definedby the inner surface part 12 of the nozzle cap 10 to be smoothly mixedwith the swirling stream S without remaining thereon, and burns. As aresult, smoke is prevented from being generated.

On the other hand, air introduced into the first auxiliary air path 6 ata position upstream thereof, not shown, passes through first auxiliaryair path 6 and the second auxiliary air path 16, as shown by a solidarrow C, and reaches the entrance 19 of the fuel-jet guide 17, fromwhich it flows along the fuel-jet guide 17 defined by the inner surfacepart 12 of the nozzle cap 10 and joins with the swirling stream S.

While this air is called cooling air because it cools the inner surfacepart 12 of the nozzle cap 10, it also has a function for preventing thefuel ejected from the one or more nozzle holes 3 on the downstream endsurface 2 of the nozzle body 1 from sticking to the inner surface part12 and being ignited there.

FIG. 2 illustrates a structure of an prior art combustor for a gasturbine having no nozzle cap 10, and a flow of fuel in such a case,wherein circulation vortices V generated behind the nozzle body 1involve part of fuel therein. The fuel remains there and generatessmoke.

As described above, the combustor for a gas turbine according to thepresent invention is provided with a nozzle cap of a generally conicalshape, diverging downstream from a jet of a nozzle body, whereby fuelejected from the jet of the nozzle body smoothly flows along the nozzlecap, without remaining there as in the prior art, resulting in no smokebeing generated.

What is claimed is:
 1. A combustor for a gas turbine comprising: anozzle body having one or more nozzle holes at the center of adownstream end wall thereof, said one or more nozzle holes being adaptedto eject fuel; a plurality of swirlers located in a space between anouter tubular body disposed around said nozzle body and said nozzlebody; and a nozzle cap having a surface of a generally conical shapediverging downstream from said one or more nozzle holes of said nozzlebody, said nozzle cap further having an upstream end surface whichextends in parallel with said downstream end wall of said nozzle body soas to define a gap therebetween forming a cooling air path, wherein fuelejected from said one or more nozzle holes is mixed with swirling airblowing from a swirl path formed by said plurality of swirlers, andwherein said surface of a generally conical shape forms a fuel-jet guidefor smoothly guiding the fuel ejected from said one or more nozzle holesinto the swirl path, and wherein said surface of a conical shape furtherdefines an inlet opening of said fuel-jet guide such that cooling airintroduced into said cooling air path flows out along the fuel-jet guidethereby cooling said fuel-jet guide.
 2. A combustor for a gas turbineaccording to claim 1, wherein a partition is provided intermediate saidplurality of swirlers and a circumference of said nozzle body to definea narrow path between said circumference of the nozzle body and saidpartition, said narrow path having a down stream end connected to saidcooling air path.